Iraqi military sources said militants killed at least 18 Iraqi officers and soldiers in Anbar province on Saturday, including a commander who oversaw a crackdown on protesters earlier this year.

The Defence Ministry said Kurwi, the assistant commander of the army's Seventh Division, and several other high-ranking officers were killed by a roadside bomb while pursuing militants from an al Qaeda training camp in Anbar's desert.

But other military sources said the officers were killed when three suicide bombers wearing explosive belts detonated themselves among them in the western town of Rutba, 360 km west of Baghdad.

A military officer who was at the scene told Reuters by phone that "all that we know so far is three suicide bombers wearing explosive vests came from nowhere and detonated themselves among the officers". While some security officials suggested informants may have lured the commanders to the area under the pretext of raiding the al Qaeda camp.

No specific group immediately claimed responsibility for the attack, but suicide bombing is the trademark of al Qaeda's Iraqi affiliate, which merged this year with counterparts in Syria to form the Islamic State of Iraq and the Levant (ISIL).